Hydraulic motor

ABSTRACT

A rotary hydraulic motor including a stator having a central cylindrical cavity with radial slots communicating with the cavity and containing reciprocable sealing rollers, a cam rotor in the cavity with a peripheral cam surface including a plurality of cam lobes with intervening lows engaging the sealing rollers to form displacement chambers, a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the sides of the stator adjacent the roller slots, an annular array of alternate inlet and outlet ports in each port plate adjacent the roller slots in the stator, and a pair of pressure plates disposed against the surfaces of the port plates remote from the rotor and the stator. Pressure chambers around the periphery of the port plates reduce deflection of the plates, and pressure chambers behind each pressure plate seal the port plates in the housing. The rotor is constructed with passages communicating the inlet ports in the two port plates and passages communicating the outlet ports in the two port plates. Provision is made for supplying pressure acting in the outer ends of the slots to urge the rollers toward the cam.

United States Patent 91 Pollman 1 Feb. 27, 1973 HYDRAULIC MOTOR [75]Inventor: Frederic W. Pollman, Rockford, Ill.

[73] Assignee: Sundstrand Corporation, Rockford,

Ill.

[22] Filed: Sept. 14, 1971 [21] Appl. No.: 180,317

[52] U.S. Cl. ..41 8/82, 418/131, 418/186, 418/225, 418/248, 418/249[51] Int. Cl ..F0lc 1/00, F03c 3/00, F04c 1/00 [58] Field ofSearch....4l8/77, 79, 82, 131, 177, 183,

[56] References Cited UNITED STATES PATENTS 1,349,353 8/1920 Wilber......418/248 2,078,887 4/1937 Wood.. ..4l8/248 3,016,021 l/1962 Rineer..418/225 3,128,708 4/1964 l-lenning .......418/249 3,606,600 9/1971Pollman ..418/131 Primary Examiner-William Freeh Assistant Examiner.lohnJ. Vrablik Attorney-Alex A. Hofgren et al.

[57] ABSTRACT A rotary hydraulic motor including a stator having acentral cylindrical cavity with I radial slots communicating with thecavity and containing reciprocable sealing rollers, a cam rotor in thecavity with a peripheral cam surface including a plurality of cam lobeswith intervening lows engaging the sealing rollers to form displacementchambers, a pair of port plates secured to opposite sides of the rotorfor rotation therewith including outwardly disposed portions slidablyengaging the sides of the stator adjacent the roller slots, an annulararray of alternate inlet and outlet ports in each port plate adjacentthe roller slots in the stator, and a pair of pressure plates disposedagainst the surfaces of the port plates remote from the rotor and thestator. Pressure chambers around the periphery of the port plates reducedeflection of the plates, and pressure chambers behind each pressureplate seal the port plates in the housing. The rotor is constructed withpassages communicating the inlet ports in the two port plates andpassages communicating the outlet ports in the two port plates.Provision is made for supplying pressure acting in the outer ends of theslots to urge the rollers toward the cam.

30 Claims, 12 Drawing Figures 26 1 /55 0 i 4 fl i w 1? '52 i102) 109 t1% \7 E .1 7

61 105 Z! 102/ 32575 70 004 104 3 J I? :2; do 71 g 4% PATENTEI] FEB 2 7I975 SHEET 3 UP 4 PATENTED P1821 3.718.411

sum 1 or 4 HYDRAULIC MOTOR BACKGROUND OF THE INVENTION The presentinvention relates to a cam motor including a rotor formed with aperipheral cam surface including cam lobes and intervening lowsrotatable in a stator chamber formed with radial slots containingreciprocable sealing rollers engaging the cam surface to providedisplacement chambers between the cam lobes. In the past, there has beensome work in connec tion with hydraulic cam motors. For example, priorU. S. Pat. Nos. 346,531, 762,126, 883,319, 2,492,687, 3,128,708 and3,276,386 relate to constructions of the type under consideration here.However, there has not been great competitive activity, and the knownprior constructions are subject to some disadvantages.

in particular, the prior art devices do not provide for both radial andaxial pressure balancing in fluid translating devices of the typedescribed. Further, the prior art devices do not provide for the portingof fluid directly to both sides of the rotor and stator so as to ensureadequate fluid flow relative to the displacement chambers. Additionally,the prior art constructions have lacked adequate means for maintainingthe sealing rollers in contact with the rotating cam surface.

SUMMARY OF THE INVENTION According to the present invention, a cam motoris provided with a cam rotor having port plates secured to oppositesides in an arrangement in which the rotor and port plates rotaterelative to a stator containing radial slots having reciprocable sealingrollers engaging the periphery of the rotor to form displacementchambers between the cam lobes on the rotor. In order to ensure adequatefluid flow relative to the displacement chambers, provision is made forporting fluid to and from the chambers at both sides of the rotor andstator by means of appropriate inlet and outlet ports provided in bothof the port plates. In order to communicate the inlet ports in the twoport plates, passages are provided through the rotor, and in order tocommunicate the outlet ports in the two port plates, other passages areprovided in the rotor.

In order to urge the sealing rollers in the stator slots toward the camsurface for engagement therewith, provision is made for applying fluidpressure in the stator slots radially outside of the sealing rollers forpurposes of creating a pressure differential acting to urge the rollerstoward the cam.

More specifically, the cam, the inlet and outlet porting in the portplates, the slots in the stator, and the sealing rollers are constructedto restrict flow in and out of the porting radially inside of therollers during contact of the rollers with low portions of the rises andfalls of the cam, and to restrict flow in and out of the porting outsideof the rollers during contact of the rollers with the high portions ofthe rises and falls of the cam, in a manner to create a pressuredifferential urging the rollers toward the cam during communication withthe inlet ports and the outlet ports, so that the rollers follow the camrises and falls.

Additionally, ports are provided between the inlet and outlet ports forsupplying fluid at intermediate pressure to the slots in the statoroutside of the rollers for urging the latter toward the cam duringintervals between communication with the inlet and outlet ports toobtain sealing with minimum load.

In order to provide for pressure balancing, the motor constructionadditionally includes a pair of pressure plates disposed respectivelybeside the port plates, each including an annular pressure chambercommunicating with inlet pressure and an annular pressure chambercommunicating with outlet pressure, to urge the pressure plates towardthe rotating assembly, thereby to seal the rotating assembly relative tothe housing.

In order to control deflection of the port plates and reduce leakage,provision is made for peripheral chambers surrounding the port platessupplied with fluid at a pressure intermediate the inlet pressure andoutlet pressure by means of leakage fluid escaping between the portplates and the stator due to clearance provided to facilitate rotationof the port plates relative to the stator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectionalview through a motor constructed according to the principles of thepresent invention, taken at about the line 11 on FIG.

FIG. 2 is a longitudinal sectional view through the motor approximatelyon the line 2-2 of FIG. 1;

FIG. 3 is a transverse sectional view, taken at about the line 3-3 ofFIG. 2, showing the rotor, the stator, and the sealing rollers;

FIG. 4 is a transverse sectional view taken at about the line 4-4 ofFIG. 2, showing the inlet and outlet recesses in the face of one portplate adjacent the rotor and stator;

FIG. 5 is a transverse sectional view, taken at about the line 55 ofFIG. 2, showing the inlet and outlet recesses in the adjacent face ofthe other port plate;

FIG.,6 is a transverse sectional view, taken at about the line 6-6 ofFIG. 2, showing the outside of the port plate illustrated in FIG. 5;

FIG. 7 is a transverse sectional view, taken at about the line 7-7 ofFIG. 2, showing the outside of the port plate illustrated in FIG. 4;

FIG. 8 is a transverse sectional view taken at about the line 8-8 ofFIG. 2, showing the inner surfaces of one of the pressure plates;

FIG. 9 is a transverse sectional view taken at about the line 99 of FIG.2, showing the outer surface of the pressure plate illustrated in FIG.8;

FIG. 10 is a transverse sectional view, taken at about the line 10-10 ofFIG. 2, showing the inside of the end housing with inlet and outletports;

FIG. 11 is a transverse sectional view taken at about the line ]l1ll ofFIG. 3, illustrating check valves in the rotor for purposes of drainingleakage from the shaft to the low pressure side of the device; and

FIG. 12 is a fragmentary transverse sectional view taken at about theline l2-l2 of FIG. 3, illustrating spring means in the stator slotsurging the sealing rollers toward the cam surface of the rotor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to thedrawings in more detail, a housing includes an end cover member 10(FIGS. 1 and 2), an end cover member 12, and an intermediate spacer orstator member 14 adapted to be held in tightly assembled relationship bymeans of appropriate bolts 15 (FIG. 3). End housing member 10 is formedto receive appropriate bearings as at 17, and end housing member 12 isprovided with bearings as at 18 which together provide rotatable supportfor a shaft 20 mounted in the bearings and including an end portion 21projecting outwardly from the housing for appropriate connection with adevice adapted to be driven when fluid under pressure is supplied to thehousing to drive the motor. The end housing is normally closed at theleft end of the motor, though it may include a threaded aperture as at22 if desired. At the right end, the housing member 12 carries anappropriate shaft seal as at 24 to prevent leakage along the shaftoutwardly of the housmg.

In order to supply hydraulic fluid to the housing and exhaust hydraulicfluid from the housing, the end housing member 10 is formed with athreaded axially extending port 26 at one side of the axis of the shaft,and an axially extending threaded port 28 at the opposite side of theaxis of the shaft. Either of the ports 26 and 28 may function as theinlet port while the other functions as the outlet port. As seen best inFIG. 10, the longitudinal passage 26 terminates in an arcuately shapedkidney-shaped port 29 and the longitudinal passage 28 terminates in anarcuate kidney-shaped port 30. The arcuate port 29 is relatively widelyspaced from the axis of the shaft, while the arcuate-shaped port 30 isrelatively closely spaced to the shaft, and the ports serve tocommunicate the fluid to and from the fluid displacement mechanism, aswill appear.

Referring now to FIG. 3, the stator member 14 is formed with a centralcylindrical cavity 32, and around the entire peripheral wall of thecavity 32, the stator member 14 is formed with a plurality of equallyspaced radially disposed slots 34 of similar configuration, each openinginto the central cavity 32. Each of the slots 34 receives a reciprocablesealing member 36 in the form of a hollow rotatable tube or roller 36.Each of the rollers 36 is urged radially inwardly of the stator memberby a coiled compression spring 37 seated in the slot 34. As best seen inFIG. 12, base of each coiled spring 37 is preferably seated in anaperture in a plate 38 which bears on the roller 36 and functions tomaintain the spring longitudinally centered in the slot 34.

A cam-shaped rotor 40 is positioned in the stator cavity 32 andconnected by splines as at 42 for rotation with the shaft 20 while freeto move a limited amount longitudinally of the shaft. The cam rotor 40is formed with a peripheral cam surface including a plurality of equallyspaced cam lobes 43, four as illustrated, and intervening lows 45between the lobes. The top surfaces of the lobes 43, as well as thesurfaces of the lows 45, are concentric about the axis of the shaft 20and provide dwell surfaces. The cam lows and the cam highs (lobes) areconnected by rises 46 at the leading edges of the lobes, and falls 47 atthe trailing edges of the lobes. The spaces between the cam lows and thewall of the cavity in the stator provide displacement chambers to whichfluid under pressure may be supplied for driving the rotor and the shaft20. The rollers 36 on the high and low dwell portions of the cam makesealing contact with the periphery of the cam and the walls of slots 34in a manner to isolate alternate high pressure and low pressure chambersaround the periphery of the cam. Provision of an even number ofdisplacement chambers provides radial balance.

Displacement is defined by the radial difference between the seals atopposite ends of the high pressure zones on the periphery of the cam,and the arrangement is such that the seal at one end of each highpressure zone occurs at a roller positioned on a high dwell on the cam,and sealing at the opposite end of the high pressure zone occurs at aroller on a low dwell portion of the cam. In this manner, thedisplacement of the device is constant and the torque flow is even. Inthe illustration of FIG. 3, high pressure areas are indicated byinclined hatching, while areas at intermediate pressure are indicated bycrossed hatching, and areas at low pressure are indicated by the absenceof hatching. It should be understood that while springs 37 have beenillustrated only in the slots at low pressure in order to avoidinterference with the hatching, springs may be utilized in each of theslots 34 for biasing each of the rollers 36 toward the cam surface ofthe rotor.

In order to port fluid to and from the displacement chambers between therotor and the stator, a pair of port plates are provided on oppositesides of the rotor as at 50 and 52 (FIGS. 1 and 2), the first of whichis shown in more detail in FIGS. 4 and 7, and the latter of which isshown in more detail in FIGS. 5 and 6. The port plates 50 and 52 areangularly aligned with the rotor 40 by means of dowel pins as at 53. Therotor and port plates are secured together by angularly spaced machinescrews as at 54. The thickness of the rotor 40 axially is slightlygreater than the thickness of the stator, and outwardly disposedportions of the port plates 50 and 52 rotate past the slot 34 in thestator. By virtue of the limited clearance between the rotating portplates and the stationary stator, there is leakage of fluid between theport plates and the stator to the periphery of the port plates which arespaced from the periphery of the surrounding housing members, therebyproviding peripheral pressure chambers as at 55 and 56 under pressure ata value intermediate the inlet pressure and the outlet pressure.

For purposes of describing the porting, it will be convenient to referto particular ports as inlet, and to refer to other ports as outlet.Accordingly, with the cam rotating clockwise as illustrated in FIG. 3,reference is made to the port 28 in the housing member 10 and the kidney30 therein as inlet porting, and reference is made to the port 26 andthe kidney 29 as outlet porting. However, it should be understood thatthe ports may be reversed, and fluid may be supplied to the motorthrough the port 26 and exhausted through the port 28.

For purposes of porting fluid under pressure to the displacementchambers, the surface of the port plate 50 adjacent to the rotor and thestator is formed with a plurality of recesses 60 which are distinguishedfrom each other by sufflxes -l, 2, 3 and 4. The ports 60 are equallyspaced angularly around the axis of the shaft 20, and equally spacedbetween the inlet ports are a plurality of outlet ports 62-1, 62-2, 62-3and 62-4. In order to supply fluid under pressure to the inlet recesses60, the recesses 60-1 and 60-3 communicate with ports as at 64 extendingthrough the plate 50, and the recesses 60-2 and 60-4 communicate withports as at 65 through the port plate 50. In order to exhaust fluid fromthe outlet recesses 62, the recesses 62-1 and 62-3 communicate withports as at 67 through the port plate 50, and the recesses 62-2 and 62-4communicate with ports as at 68 through the port plate 50. Asillustrated in FIG. 7, the remote side of the port plate 50 i from therotor and stator is formed with an inner annular groove as at 70communicating with the inlet ports 64 and 65 in order to supply fluid tothe recesses 60. A radially outwardly disposed annular groove 71communicates with the outlet ports 67 and 68 in order to exhaust fluidfrom the outlet recesses 62.

As best seen in FIGS. 1 and 2, pressure plates 74 and 76 are disposedoutwardly from the port plates 50 and 52. In order to port fluid to theinlet groove 70 in the port plate 50, the pressure plate 74 has asurface in contact with the port plate 50 formed with an inner annulargroove as at 78 (FIG. 8) in register with the inner annular groove 70 inthe port plate. Similarly, the pressure plate includes an outer annulargroove 79 in register with the outer annular groove 71 in the port plate50. Fluid is ported from the inlet 30,28 to the groove 78 through anarcuate kidney-shaped port as at 80. Fluid is ported from the outerannular groove 79 in the pressure plate 74 to the outlet port 26,29through an arcuate kidney-shaped port 82 in the pressure plate, whichmay be in two sections if desired. The-pressure plate 70 is preferablyretained in the housing member 10 against rotation by means of a pair ofdowel pins as at 84 (FIG. 2). Similarly, the pressure plate 76 isretained in position by dowel pins as at 86.

In operation, it will be understood that the housing member 10 isstationary and the pressure plate 74 is retained against rotation, whilethe rotor 40 and the port plate 50 are rotatable with the shaft 20.Fluid under pressure supplied through the inlet port 28,30 flows throughthe arcuate porting 80 to the annular channel between the pressure plate74 and the port plate 50 provided by the annular groove 78 in thepressure plate and the annular groove 70 in the port plate. In thismanner, the annular channel functions as an inlet manifold for supplyingfluid under pressure to the rotating inlet ports 64 and 65 in the portplate 50, so that the inlet recesses 60 contain fluid under pressure.The fluid under pressure in the inlet recesses 60 is supplied to thedisplacement chambers between the rotor 40 and the stator 14 at thespaces between the cam lobes 43. The fluid under pressure acting on thecam surfaces 47 forces the rotor to turn, and the rotor causes rotationof the port plates and the shaft 20. Thus, the high pressuredisplacement chambers between the rotor and the'stator rotate with therotor, and the rotor is driven with an even torque flow.

The inlet and outlet recesses 60 and 62 in the face of the port plate 50have distinctive configurations. The basic configuration of each recess60 corresponds to that illustrated at 60-4, which includes an outerkidney portion 60a adapted to communicate with the outer portions of theroller slots 34 as the port plate rotates, an inner inclined kidneyportion 60b which conforms approximately to the cam fall portion 47 andcommunicates with the inner portions of the roller slots 34 in thestator, an intermediate radially disposed connecting channel 60c, and aradially inwardly directed channel 60d through which the inlet portsextend to the opposite face of the port plate. The configuration of theinlet recess 60-2 corresponds to that of the' inlet recess 60-4. Theconfiguration of inlet recesses 60-1 and 60-3 is similar to that at60-4, except that the inner channel d in recesses 60-1 and 60-3 issomewhat wider to accommodate ports 64 which are larger than ports 65.

In order to ensure adequate flow of fluid to and from the displacementchambers, the port plate 56 on the opposite side of the rotor is alsoformed with inlet and outlet recesses similar to those at 60 and 62 inthe face of the port plate 50. In order to port fluid through the rotor40 to the inlet recesses in the port plate 56, there are passages 88 and89 extending through the rotor and communicating with ports 64, whichare larger than ports 65 in order to convey adequate fluid to both sidesof the rotor.

The basic configuration of the outlet recesses 62 in the face of theport plate 50 is that at 62-1 and 62-3 which includes an outwardlylocated kidney 62a, and inwardly disposed kidney 62b which is inclinedto follow the inclination of the cam rise surfaces 46, and a connectingradially disposed channel 620 through which outlet ports 67 and 68extend. Recesses 62-2 and 62-4 include a radially inwardly directedchannel 62d.

In order to convey outlet fluid through the rotor between the outletrecesses in the port plate 52 and the port plate 50, the rotor is formedwith passages 91 and 92 communicating respectively with the inwardlyprojecting portions 62d of the outlet recesses 62-2 and 62-4.

The inlet recesses in the face of the port plate 52 are designated -1,100-2, 100-3 and 100-4, and the shapes correspond to those at 60-1,60-2, 60-3 and 60-4 in the face of the port plate 50, except that theinwardly extending leg 100d of the inlet recess 100-4 in the face of theport plate 52 includes a finger extension 100e which functions as acheck valve outlet for a purpose that will appear presently.

The outlet recesses in the face of the port plate 56 are designated102-1, 102-2, 102-3 and 102-4, and the configuration of such recessesconforms substantially to the configuration of corresponding outletrecesses 62-1, 62-2, 62-3 and 62-4 in the face of the port plate 50,except that the recess 102-3 has an inwardly extending leg 102 withfinger 102e adapted to communicate with a check valve outlet forpurposes that will appear.

In order to properly distribute inlet fluid, the recesses 100-1 and100-3 contain ports as at 104 through the port plate 52, and therecesses 100-2 and 100-4 include ports 105 through the port plate 52. Inorder to communicate the ports 104 and 105 with each other, the pressureplate 76 is formed like the pressure plate 74 with an inner annulargroove 106.

In order to properly distribute outlet fluid, the outlet recesses 102-1and 102-3 are formed with ports 107 through the port plate 52, and theoutlet recesses 102-2 and 102-4 are formed with outlet ports 108. Inorder to communicate the port 107 and the port 108 with each other, theycommunicate with an outer annular groove 109 in the face of the pressureplate 76.

In operation of the motor, there is some leakage of fluid at highpressure from the inlet recesses 60 and the inlet recesses 100 radiallyoutwardly between the port plates and the stator so that fluidaccumulates in the peripheral chambers 55 and 56 around the periphery ofport plates and the pressure plates. There is some pres sure drop in theprocess of such leakage, but the pressure is higher than the pressure inthe inlet recesses 62 and 102 in the faces of the port plates, so thatthere is some leakage from the peripheral chambers 55 and 56 to therecesses 62 and 102. The pressure in the peripheral chambers 55 and S6is thus left at an intermediate value between the value of the highinlet pressure and the value of the low outlet pressure, and may be ashigh as 75 percent of inlet pressure.

The pressure of fluid in the peripheral chambers 55 and 56 is utilizedfor several purposes. More particularly, it will be understood that whenthe housing port 26 is utilized as the inlet port, the outer annulargrooves 79 and 109 in the pressure plates 74 and 76 are at high pressurewhich tends to resist deflection of the port plates due to pressurebetween the port plates and the stator. On the other hand, when the port26 is the outlet port and the pressure in the outer annular grooves 78and 106 is low pressure, the intermediate pressure in the peripheralchambers 55 and 56 tends to leak to the channels 79 and 109 and servesto resist deflection of the port plates.

Additionally, the pressure at intermediate value in the peripheralchambers 55 and 56 is utilized to aid in holding the sealing rollers 36against the periphery of the cam surface. More particularly, the portplates 50 and 52 are formed with radially disposed channels leading fromthe periphery of the port plate as at 120 at angularly spaced positionsbetween the inlet and outlet recesses. Each radially extending channel120 communicates with a kidney-shaped recess as at 122, and each of thekidneys 122 is radially positioned so that it communicates successivelywith outer portions of the radial slots 34 in the stator radiallyoutwardly from the sealing rollers 36 so that intermediate pressure isdelivered to the outer ends of the slots to urge the sealing rollerstoward the cam surface. The use of intermediate pressure assures thatthe rollers provide sealing while imposing a minimum resistance torotation.

In order to aid in holding the sealing rollers 36 against the camsurface of the rotor during communication with the inlet recesses andthe outlet recesses, the porting is formed in a manner to create apressure differential which includes a greater pressure radiallyoutwardly from the roller urging the roller to maintain contact with thecam surface. In order to obtain the pressure differential, when therollers are on the lower half of the rises and falls of the cam, axialflow in and out of the displacement chambers and the roller slots isrestricted at positions radially inwardly from the rollers. When therollers are positioned on the upper half of the rises and falls in thecam, axial flow in and out of the displacement chambers and the roller.slots is restricted radially outwardly from the rollers.

Considering first the pressure differential acting on the rollersexposed to low pressure adjacent the outlet ports, shown in FIG. 3 atapproximately 30, 1 10, 210 and 290 from the upper center of the figure,it will be understood that as the cam rotates in a clockwise direction,it has the effect of forcing low pressure fluid axially out of thedisplacement chambers and the roller slots. Considering the roller at30, for example, communicating with the outlet recesses 62-1 and 102-1,and located at the bottom of a cam rise 46 which it is about to climb,during contact of the roller with the upper half of the cam rise, axialflow from the roller slot radially outwardly from the roller isrestricted relative to axial flow out radially inwardly from the roller,as a result of which the pressure tends to be greater on the outside ofthe roller to hold the roller against the cam surface at a time when itbecomes a sealing roller, performing a function like that illustrated at10. During contact of the roller with the lower half of the cam rise,axial flow from the displacement chamber and the roller slot isrestricted relative to axial flow from the roller slot radiallyoutwardly from the roller as a result of which the pressure tends to begreater under the roller and to lift the roller from the cam. However,at that moment, the roller is not a sealing roller as are the rollers onopposite sides of it, and it is of no consequence if the roller islifted from the cam.

Considering now the rollers exposed to high pressure and at the top of acam lobe, about to ride down a fall 47, such as the roller situated atin FIG. 3, inlet fluid at high pressure, as in the inlet recesses 60-1and -1, tends to flow axially inwardly into the displacement chamber andthe roller slot. As the roller rides down the lower half of the fall inthe cam, flow axially into the displacement chamber and the roller slotis restricted inwardly of the roller relative to the in-flow outwardlyof the roller, as a result of which the pressure tends to be greaterradially outwardly from the roller to urge the latter toward the camsurface and maintain contact as it approaches a sealing functioncomparable to that of the roller illustrated at 50. As the roller ridesdown the upper half of the fall of the cam, axial flow into thedisplacement chamber and the roller slot tends to be restrictedoutwardly of the roller relative to the flow permitted inwardly of theroller as a result of which there tends to be a greater pressureunderneath the roller lifting it off the cam, but at the moment theroller is not performing a sealing function and the seemingly adverseeffect is of no consequence.

The flow restriction described above is a function of the portingprovided by the cooperating action of the cam surface, the inlet andoutlet recesses in the port plates, the roller slots and the rollers inthe slots as the cam and the port plates rotate past the roller slotsand the rollers. Referring to FIG. 5, where the cam and port plateswould be rotating in a counterclockwise direction, and viewing theoutlet recess 102-1, it can be seen that during contact of the rollerwith the lower half of the cam rise, flow axially outwardly from beneaththe roller is restricted (due to limited access of the roller peripherywith the kidney 102b) relative to flow axially outwardly from the roller(where a substantial length of slot 34 communicates with kidney 102a andchannel 102c). Similarly, during the fall of the roller while passingthe inlet port 100-4, flow axially into the chamber underneath theroller is restricted relative to flow axially into the slot radiallyoutwardly from the roller. In order to aid in restricting flow axiallyinwardly and outwardly beneath each roller during contact with the lowerhalf of each cam rise and fall, the radially inner end of each inlet andoutlet kidney 60b, 62b, 100k and l02b in port plates 50 and 52 isshallow (as indicated at 60f, 62f, 100f and 102]) relative to theremainder of the kidney with which it is associated. On the other hand,as the roller rides the upper half of the cam rises and falls, theroller itself is deep in the roller slot as a result of which access tothe roller slot is restricted. In order to aid in restricting flowaxially inwardly and outwardly radially outside each roller duringcontact with the upper half of each cam rise and fall, the end of eachinlet and outlet kidney 60a, 62a, 100a and 102a adjacent the cam lobes43 is shallow (as indicated at 60g, 62g, 100g and 102g) relative to theremainder of the kidney with which is is associated.

In order to urge the pressure balance plates 74 and 76 against the portplates 50 and 52 for purposes of sealing the port plates relative to thehousing, an inner annular pressure chamber is formed on each plate at130 (FIG. 9) between an inner annular O-ring 132 and an intermediateannular O-ring 134. The annular chamber 130 on plate 74 communicateswith the inlet pressure porting 28,30 (FIG. 1) in the housing member 10to provide a sealing force urging the pressure plate 74 toward the portplates. The chamber 130 on plate 76 communicates with inlet pressurechannel 106 through one or more ports as at 135 (FIG. 1). An outerannular chamber is provided at 136 (FIG. 9) between the intermediateO-ring 134 and an outer O-ring 138. The annular chamber 136 on plate 74communicates with the outlet porting 26,29 (FIG. 1) in the housingmember 10 to provide a force urging the pressure plate toward the portplates when the motor operation is reversed. Chamber 136 on plate 76communicates with outlet groove 109 (FIG. 1) through ports as at 137.

In order to equalize pressure at opposite ends of the splined connectionof the rotor to the shaft 20, the port plates 55 and 56 are each formedwith a groove in the face of the plate adjacent the rotor, leadingradially outwardly from the shaft cavity as at 140 for purposes ofcommunicating with an axial passage 142 through the rotor.

In order to drain the shaft cavity of leakage fluid and prevent build-upof excessive pressure therein, the shaft cavity communicates with a pairof check valves 150 and 1152 (FIG. 11), one adapted to communicate withthe inlet porting and one adapted to communicate with the outletporting, so that the shaft cavity may be drained to the low pressureside of the system. The check valve 150 includes an axial bore 153 inthe rotor 40 receiving a ball valve member spring-urged toward an inletseat communicating with the shaft cavity by means of a radial groove 154in the face of the port plate 50. Theoutlet end .of the check valve 150communicates with the finger 102e (FIG. 5) extending from the outletrecess 102-3.

The check valve 152 includes an axial bore 156 in the rotor 40 receivinga ball member spring-urged toward an inlet seat communicating with theshaft cavity through a radial groove 157 in the face of the port plate50. The outlet from the check valve 156 communicates with the finger le(FIG. extending from the inlet recess 1024. It will be understood thatany undue pressure increase in fluid in the shaft cavity will bepermitted to escape through the check valve 150 or 152 which allowscommunication with low pressure.

I claim:

1. A rotary hydraulic fluid translating device, comprising, I

a. a housing,

b. a stator in the housing having a cylindrical cavity and a pluralityof radially disposed slots with reciprocable sealing members therein,

c. a rotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes engageable with the sealing membersto form displacement chambers,

a pair of plates secured to opposite sides of the rotor for rotationtherewith including outwardly disposed portions slidably engaging thestator adjacent the slots therein and peripheral portions spaced fromthe surrounding housing to define peripheral pressure chambers,

e. an annular array of alternate inlet and outlet ports extendingthrough one plate in communication with the cavity and slots in thestator,

f. means in the housing providing an inlet communicating with the inletports and an outlet communicating with the outlet ports as the rotor andthe plates rotate, and

g. leakage paths between the stator and the rotating plates leading tothe peripheral pressure chambers creating pressure in the chambers at avalue intermediate the values of inlet and outlet pressures.

2. A rotary hydraulic fluid translating device as defined in claim 1,including passages porting intermediate pressure from the peripheralchambers to the slots in the stator radially outwardly from the sealingmembers.

3. A rotary hydraulic fluid translating device as defined in claim 1,including means providing a pressure differential across the sealingmembers acting in the outer ends of the slots tending to hold themembers on the cam.

4. A rotary hydraulic motor, comprising,

a. a housing,

b. a stator in the housing having a central cylindrical cavity and aplurality of radial slots extending from the cavity with reciprocablesealing rollers therein,

c. a rotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes and intervening lows engaging thesealing rollers to form displacement chambers between the lobes,

d. a pair of port plates secured to opposite sides of the rotor forrotation therewith including outwardly disposed portions slidablyengaging the sides of the stator adjacent the slots and peripheralportions spaced from the surrounding housing to define peripheralpressure chambers,

e. a shaft mounted in the housing and rotatable with the rotor and portplates,

f. an annular array of alternate inlet and outlet ports extendingthrough each port plate in communication with the cavity and slots inthe stator,

g. means in the housing providing an annular inlet groove communicatingwith the inlet ports and an annular 'outlet groove communicating withthe outlet ports on rotation of the rotor and port plates, and

h. leakage paths between the stator and the port plates leading to theperipheral pressure chambers to provide pressure in the chambers at avalue intermediate the inlet and outlet pressures and act ing on thesurface of the port plates remote from the stator to reduce deflectionof the plates.

5. A rotary hydraulic motor as defined in claim 4, including passagesthrough the rotor communicating the inlet ports in the two port plateswith each other and communicating the outlet ports in the two plateswith each other.

6. A rotary hydraulic motor as defined in claim 4, ineluding,

a. a pair of pressure plates disposed respectively against the surfaceof the port plates remote from the rotor and stator,

. an inlet kidney through one pressure plate communicating with theannular inlet groove and an outlet kidney through one pressure platecommunicating with the annular outlet groove,

c. means defining an annular pressure balance chamber behind eachpressure plate in communication with inlet pressure, and

. means defining an annular pressure chamber behind each pressure platein communication with outlet pressure.

7. A rotary hydraulic motor as defined in claim 6, including passages ineach port plate porting intermediate pressure from the peripheralchambers to the slots in the stator radially outwardly from the sealingrollers.

8. A rotary hydraulic fluid translating device, comprising,

a. a housing,

b. a stator in the housing having a cylindrical cavity and a pluralityof radially disposed slots with reciprocable sealing members therein,

c. a rotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes engageable with the sealing membersto from displacement chambers,

d. a pair of plates secured to opposite sides of the rotor for rotationtherewith including outwardly disposed portions slidably engaging thestator adjacent the slots therein and peripheral portions spaced fromthe surrounding housing to define peripheral pressure chambers atpressure intermediate inlet and outlet pressures,

e. an annular array of alternate inlet and outlet ports extendingthrough one plate in communication with the cavity and slots in thestator,

f. means in the housing adjacent the surface of the ported plate remotefrom the rotor providing an annular inlet groove communicating with theinlet ports and an annular outlet groove communicating with the outletports as the ported plate rotates, and

g. passages porting intermediate pressure from one peripheral chamber tothe slots in the stator radially outwardly from the sealing membersbetween the inlet and outlet ports.

9. A rotary hydraulic fluid translating device as defined in claim 8,including means creating a pressure differential across the sealingmembers during exposure to the inlet and outlet ports acting in theouter ends of the slots to urge the members toward the cam.

10. A rotary hydraulic fluid translating device, comprising,

a. a housing,

b. a stator in the housing having a cylindrical cavity and a pluralityof radially disposed slots with reciprocable sealing members therein,

c. a rotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes engageable with the members to formdisplacement chambers between the lobes,

d. a pair of plates secured to opposite sides of the rotor for rotationtherewith including outwardly disposed portions slidably engaging thestator adjacent the slots therein,

e. an annular array of alternate inlet and outlet recesses in the faceof each plate adjacent the slots in the stator,

f. an annular array of alternate inlet and outlet ports extendingthrough each plate in communication with the recesses in such plates,

. means in the housing providing an inlet communicating with the inletports and an outlet communicating with the outlet ports as the rotor andthe plates rotate, and

. passages through the rotor communicating the inlet recesses in saidone plate with the inlet recesses in the other plate, and communicatingthe outlet recesses in said one plate with the outlet recesses in theother plate.

11. A rotary hydraulic fluid translating device as defined in claim 10,wherein,

a. peripheral portions of the rotating plates are spaced from thesurrounding housing to define peripheral pressure chambers, and

. leakage paths between the stator and the rotating plates lead to theperipheral pressure chambers to create pressure therein at a valueintermediate inlet and outlet pressures acting on the surface of theplates remote from the stator to reduce deflection of the plates.

12. A rotary hydraulic fluid translating device as defined in claim 10including passages in each plate for porting intermediate pressure tothe slots in the stator radially outwardly of the sealing members.

13. A rotary hydraulic fluid translating device as defined in claim 10including means creating a pressure differential across the sealingmembers during exposure to the inlet and outlet ports acting in theouter ends of the slots to urge the members toward the cam.

14. A rotary hydraulic fluid translating device, comprising,

a. a housing,

b. a stator in the housing having a cylindrical cavity and a pluralityof radially disposed slots with reciprocable sealing members therein,

c. a rotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes and intervening lows engaging thesealing members in the stator to form displacement chambers,

. a pair of plates secured to opposite sides of the rotor for rotationtherewith including outwardly disposed portions slidably engaging thestator adjacent the slots therein,

e. an annular array of alternate inlet and outlet recesses in the faceof one plate adjacent the slots in the stator and extending radially adistance from the outer end of the slots inwardly to the cam lows tosupply and exhaust fluid relative to the displacement chambers and theslots,

f. an annular array of inlet ports extending through said one plate incommunication with the inlet recesses and a radially spaced annulararray of outlet ports through the plate in communication with the outletrecesses, and

. means in the housing at the opposite face of said one plate providingan annular inlet groove communicating with the inlet ports and aradially spaced annular outlet groove communicating with the outletports as the rotor and the plates rotate.

15. A rotary hydraulic fluid translating device as defined in claim 14,wherein the sealing members are rollers having a diameter slightly lessthan the width of the slots.

16. A rotary hydraulic fluid translating device as defined in claim 14,wherein, p

a. peripheral portions of the rotating plates are spaced from thesurrounding housing to define peripheral pressure chambers, and

b. leakage paths between the stator and the rotating plates lead to theperipheral pressure chambers to create pressuretherein at a valueintermediate inlet and outlet pressures acting on the surface of theplates remote from the stator to reduce deflection of the plates.

17. A rotary hydraulic fluid translating device as defined in claim 16,including passages porting intermediate pressure from the peripheralchambers to the slots in the stator radially outwardly from the sealingmembers.

'18. A rotary hydraulic fluid translating device, comprising,

' a. a housing,

b. a stator in the housing having a cylindrical cavity and a pluralityof radial slots with reciprocable sealing rollers therein,

c. a rotor disposed in the stator cavity and having a peripheral camsurface including a plurality of cam lobes and intervening lowsconnected by rises and falls engaging the sealing rollers to formdisplacement chambers,

d. a pair of plates secured to opposite sides of the rotor for rotationtherewith including outwardly disposed portions slidably engaging thestator adjacent the slots therein, 7

e. an annular array of alternate inlet and outlet recesses in the faceof one plate adjacent the slots in the stator and extending radially adistance from the outer end of the slots inwardly to the cam lows tosupply and exhaust fluid relative to the displacement chambers and theslots,

f. an annular array of alternate inlet and outlet ports extendingthrough said one plate in communication with the inlet and outletrecesses, respectively,

. means in the housing at the opposite face of said one plate providingan annular inlet groove communicating with the inlet ports and anannular outlet groove communicating with the outlet ports on rotation ofthe rotor and plates, and

b. means creating a pressure differential across the sealing rollersacting in the outer ends of the slots to urge the rollers toward thecam.

19. A rotary hydraulic translating device as defined in claim 18,including springs in the slots urging the rollers toward the camsurface.

20. A rotary hydraulic fluid translating device as defined in claim 18including means restricting flow in and out of said recesses inwardly ofsaid rollers during contact of the rollers with lower portions of thecam rises and falls, and means restricting flow in and out of saidrecesses outwardly of said rollers during contact of the rollers withupper portions of the cam rises and falls.

211. A rotary hydraulic fluid translating device as defined in claim 20including ports in said one plate intermediate the inlet and outletrecesses for supplying pressure to the slots in the stator radiallyoutwardly from the sealing rollers.

22. A rotary hydraulic motor, comprising,

a. a housing,

b. a stator in the housing having a central cylindrical cavity and aplurality of radial slots extending from the cavity with loosely fittingreciprocable sealing rollers therein,

c. a rotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes and intervening lows engaging thesealing rollers to form displacement chambers,

d. a pair of port plates secured to opposite sides of the rotor forrotation therewith including outwardly disposed portions slidablyengaging the sides of the stator adjacent the slots and peripheralportions spaced from the surrounding housing to define peripheralpressure chambers,

e. a shaft mounted in the housing and rotatable with the rotor and portplates,

f. an annular array of alternate inlet and outlet recesses in the faceof each port plate adjacent the slots in the stator,

g. an annular array of alternate inlet and outlet ports extendingthrough each plate in communication with the recesses in such plate,

h. means providing an inlet communicating with the inlet ports and anoutlet communicating with the outlet ports on rotation of the cam andport plates, and

i. said inlet and outlet recesses, said cam, said slots and said rollersbeing constructed to restrict flow in an out of said recesses inwardlyof the rollers during contact of the rollers with low portions of therises and falls of the cam, and to restrict flow in and out of saidrecesses outwardly of the rollers during contact of the rollers with thehigh portions of the rises and falls of the cam, thereby to create apressure differential acting across the rollers acting in the outer endsof the slots to urge the rollers toward the cam.

23. A rotary hydraulic motor as defined in claim 22, including means forporting pressure to the slots radially outwardly from the rollersintermediate the inlet and outlet recesses.

24. A rotary hydraulic motor as defined in claim 23, including springmeans in the slots urging the sealing rollers toward the cam surface.

25. A rotary hydraulic fluid translating device, comprising,

a. a housing,

b. a stator in the housing having a cylindrical cavity and a pluralityof radially disposed slots with reciprocable sealing members therein,

c. a rotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes engageable with the sealing membersin the stator to form displacement chambers between the lobes,

d. a pair of port plates secured to opposite sides of the rotor forrotation therewith including outwardly disposed portions slidablyengaging the stator adjaent the slots therein and peripheral portionsspaced from the surrounding housing to define peripheral pressurechambers,

e. an annular array of alternate inlet and outlet ports extendingthrough each plate in communication with the cavity and slots in thestator,

f. a pair of pressure plates disposed respectively against the surfacesof the port plates remote from the rotor and stator,

means at each interface of the port plates and pressure plates providingan annular inlet groove communicating with the inlet ports and anannular outlet groove communicating with the outlet ports as the rotorand the plates rotate,

. an inlet kidney through each pressure plate communicating with theadjacent annular inlet groove and an outlet kidney through each pressureplate communicating with the adjacent annular outlet groove,

i. means defining an annular pressure chamber behind each pressure platein communication with the inlet port therein and means defining anannular pressure chamber behind each pressure plate in communicationwith the outlet port therein, and

j. leakage paths between the stator and the rotating plates leading tothe peripheral pressure chambers creating pressure in the chambers at avalue intermediate the values of inlet and outlet pressures.

26. A rotary hydraulic fluid translating device as defined in claim 25,including passages in each port plate porting intermediate pressure fromthe peripheral chambers to the slots in the stator radially outwardlyfrom the sealing members between inlet and outlet recesses.

27. A rotary hydraulic fluid translating device as defined in claim 25,including passages through the rotor communicating the inlet ports inthe two port plates with each other and communicating the outlet portsin the two port plates with each other.

28. A rotary hydraulic motor, comprising,

a. a housing,

b. a stator in the housing having a central cylindrical cavity and aplurality of radial slots extending from the cavity with loosely fittingreciprocable sealing rollers therein,

c. a rotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes and intervening lows engaging thesealing rollers to form displacement chambers,

. a pair of port plates secured to opposite sides of the rotor forrotation therewith including outwardly disposed portions slidablyengaging the sides of the stator adjacent the slots and peripheralportions spaced from the surrounding housing to define peripheralpressure chambers,

e. a shaft mounted in the housing and rotatable with the rotor and portplates f. an annular array of alternate inlet and outlet recesses in theface of each port plate adjacent the slots in the stator,

. an annular array of alternate inlet and outlet ports extending througheach plate in communication with the recesses in such plate,

. a pair of pressure plates disposed respectively against the surfacesof the port plates remote from the rotor and stator,

. means at each interface of the port plates and pressure platesproviding an annular inlet groove communicating with the inlet ports andan annular outlet groove communicating with the outlet ports as therotor and the plates rotate,

j. an inlet kidney through each pressure plate communicating with theadjacent annular inlet groove, and an outlet kidney through eachpressure plate communicating with the adjacent annular outlet groove,and

k. means defining an annular pressure chamber behind each pressure platein communication with the inlet port therein and means defining anannular pressure chamber behind each pressure plate in communicationwith the outlet port therein.

29. A rotary hydraulic motor as defined in claim 28, wherein thealternate inlet and outlet recesses in the face of each plate extendradially a distance from the outer end of the slots in the statorinwardly to the cam lows, wherein the annular array of inlet portsthrough each port plate is radially spaced from the annular array ofoutlet ports through such plate and wherein the annular inlet groove ateach interface of the port plates and pressure plates is radially spacedfrom the annular outlet groove at each interface of the port plates andpressure plates.

30. A rotary hydraulic motor as defined in claim 28, including passagesthrough the rotor communicating the inlet recesses in the two portplates with each other and communicating the outlet recesses in the twoport plates with each other.

1. A rotary hydraulic fluid translating device, comprising, a. ahousing, b. a stator in the housing having a cylindrical cavity and aplurality of radially disposed slots with reciprocable sealing memberstherein, c. a rotor disposed in the stator cavity having a peripheralcam surface including a plurality of cam lobes engageable with thesealing members to form displacement chambers, d. a pair of platessecured to opposite sides of the rotor for rotation therewith includingoutwardly disposed portions slidably engaging the stator adjacent theslots therein and peripheral portions spaced from the surroundinghousing to define peripheral pressure chambers, e. an annular array ofalternate inlet and outlet ports extending through one plate incommunication with the cavity and slots in the stator, f. means in thehousing providing an inlet communicating with the inlet ports and anoutlet communicating with the outlet ports as the rotor and the platesrotate, and g. leakage paths between the stator and the rotating platesleading to the peripheral pressure chambers creating pressure in thechambers at a value intermediate the values of inlet and outletpressures.
 2. A rotary hydraulic fluid translating device as defined inclaim 1, including passages porting intermediate pressure from theperipheral chambers to the slots in the stator radially outwardly fromthe sealing members.
 3. A rotary hydraulic fluid translating device asdefined in claim 1, including means providing a pressure differentialacross the sealing members acting in the outer ends of the slots tendingto hold the members on the cam.
 4. A rotary hydraulic motor, comprising,a. a housing, b. a stator in the housing having a central cylindricalcavity and a plurality of radial slots extending from the cavity withreciprocable sealing rollers therein, c. a rotor disposed in the statorcavity having a peripheral cam surface including a plurality of camlobes and intervening lows engaging the sealing rollers to formdisplacement chambers between the lobes, d. a pair of port platessecured to opposite sides of the rotor for rotation therewith includingoutwardly disposed portions slidably engaging the sides of the statoradjacent the slots and peripheral portions spaced from the surroundinghousing to define peripheral pressure chambers, e. a shaft mounted inthe housing and rotatable with the rotor and port plates, f. an annulararray of alternate inlet and outlet ports extending through each portplate in communication with the cavity and slots in the stator, g. meansin the housing providing an annular inlet groove communicating with theinlet ports and an annular outlet groove communicating with the outletports on rotation of the rotor and port plates, and h. leakage pathsbetween the stator and the port plates leading to the peripheralpressure chambers to provide pressure in the chambers at a valueintermediate the inlet and outlet pressures and acting on the surface ofthe port plates remote from the stator to reduce deflection of theplates.
 5. A rotary hydraulic motor as defined in claim 4, includingpassages through the rotor communicating the inlet portS in the two portplates with each other and communicating the outlet ports in the twoplates with each other.
 6. A rotary hydraulic motor as defined in claim4, including, a. a pair of pressure plates disposed respectively againstthe surface of the port plates remote from the rotor and stator, b. aninlet kidney through one pressure plate communicating with the annularinlet groove and an outlet kidney through one pressure platecommunicating with the annular outlet groove, c. means defining anannular pressure balance chamber behind each pressure plate incommunication with inlet pressure, and d. means defining an annularpressure chamber behind each pressure plate in communication with outletpressure.
 7. A rotary hydraulic motor as defined in claim 6, includingpassages in each port plate porting intermediate pressure from theperipheral chambers to the slots in the stator radially outwardly fromthe sealing rollers.
 8. A rotary hydraulic fluid translating device,comprising, a. a housing, b. a stator in the housing having acylindrical cavity and a plurality of radially disposed slots withreciprocable sealing members therein, c. a rotor disposed in the statorcavity having a peripheral cam surface including a plurality of camlobes engageable with the sealing members to from displacement chambers,d. a pair of plates secured to opposite sides of the rotor for rotationtherewith including outwardly disposed portions slidably engaging thestator adjacent the slots therein and peripheral portions spaced fromthe surrounding housing to define peripheral pressure chambers atpressure intermediate inlet and outlet pressures, e. an annular array ofalternate inlet and outlet ports extending through one plate incommunication with the cavity and slots in the stator, f. means in thehousing adjacent the surface of the ported plate remote from the rotorproviding an annular inlet groove communicating with the inlet ports andan annular outlet groove communicating with the outlet ports as theported plate rotates, and g. passages porting intermediate pressure fromone peripheral chamber to the slots in the stator radially outwardlyfrom the sealing members between the inlet and outlet ports.
 9. A rotaryhydraulic fluid translating device as defined in claim 8, includingmeans creating a pressure differential across the sealing members duringexposure to the inlet and outlet ports acting in the outer ends of theslots to urge the members toward the cam.
 10. A rotary hydraulic fluidtranslating device, comprising, a. a housing, b. a stator in the housinghaving a cylindrical cavity and a plurality of radially disposed slotswith reciprocable sealing members therein, c. a rotor disposed in thestator cavity having a peripheral cam surface including a plurality ofcam lobes engageable with the members to form displacement chambersbetween the lobes, d. a pair of plates secured to opposite sides of therotor for rotation therewith including outwardly disposed portionsslidably engaging the stator adjacent the slots therein, e. an annulararray of alternate inlet and outlet recesses in the face of each plateadjacent the slots in the stator, f. an annular array of alternate inletand outlet ports extending through each plate in communication with therecesses in such plates, g. means in the housing providing an inletcommunicating with the inlet ports and an outlet communicating with theoutlet ports as the rotor and the plates rotate, and h. passages throughthe rotor communicating the inlet recesses in said one plate with theinlet recesses in the other plate, and communicating the outlet recessesin said one plate with the outlet recesses in the other plate.
 11. Arotary hydraulic fluid translating device as defined in claim 10,wherein, a. peripheral portions of the rotating plates are spaced fromthe surrounding housing to define peripheral pressure chamberS, and b.leakage paths between the stator and the rotating plates lead to theperipheral pressure chambers to create pressure therein at a valueintermediate inlet and outlet pressures acting on the surface of theplates remote from the stator to reduce deflection of the plates.
 12. Arotary hydraulic fluid translating device as defined in claim 10including passages in each plate for porting intermediate pressure tothe slots in the stator radially outwardly of the sealing members.
 13. Arotary hydraulic fluid translating device as defined in claim 10including means creating a pressure differential across the sealingmembers during exposure to the inlet and outlet ports acting in theouter ends of the slots to urge the members toward the cam.
 14. A rotaryhydraulic fluid translating device, comprising, a. a housing, b. astator in the housing having a cylindrical cavity and a plurality ofradially disposed slots with reciprocable sealing members therein, c. arotor disposed in the stator cavity having a peripheral cam surfaceincluding a plurality of cam lobes and intervening lows engaging thesealing members in the stator to form displacement chambers, d. a pairof plates secured to opposite sides of the rotor for rotation therewithincluding outwardly disposed portions slidably engaging the statoradjacent the slots therein, e. an annular array of alternate inlet andoutlet recesses in the face of one plate adjacent the slots in thestator and extending radially a distance from the outer end of the slotsinwardly to the cam lows to supply and exhaust fluid relative to thedisplacement chambers and the slots, f. an annular array of inlet portsextending through said one plate in communication with the inletrecesses and a radially spaced annular array of outlet ports through theplate in communication with the outlet recesses, and g. means in thehousing at the opposite face of said one plate providing an annularinlet groove communicating with the inlet ports and a radially spacedannular outlet groove communicating with the outlet ports as the rotorand the plates rotate.
 15. A rotary hydraulic fluid translating deviceas defined in claim 14, wherein the sealing members are rollers having adiameter slightly less than the width of the slots.
 16. A rotaryhydraulic fluid translating device as defined in claim 14, wherein, a.peripheral portions of the rotating plates are spaced from thesurrounding housing to define peripheral pressure chambers, and b.leakage paths between the stator and the rotating plates lead to theperipheral pressure chambers to create pressure therein at a valueintermediate inlet and outlet pressures acting on the surface of theplates remote from the stator to reduce deflection of the plates.
 17. Arotary hydraulic fluid translating device as defined in claim 16,including passages porting intermediate pressure from the peripheralchambers to the slots in the stator radially outwardly from the sealingmembers.
 18. A rotary hydraulic fluid translating device, comprising, a.a housing, b. a stator in the housing having a cylindrical cavity and aplurality of radial slots with reciprocable sealing rollers therein, c.a rotor disposed in the stator cavity and having a peripheral camsurface including a plurality of cam lobes and intervening lowsconnected by rises and falls engaging the sealing rollers to formdisplacement chambers, d. a pair of plates secured to opposite sides ofthe rotor for rotation therewith including outwardly disposed portionsslidably engaging the stator adjacent the slots therein, e. an annulararray of alternate inlet and outlet recesses in the face of one plateadjacent the slots in the stator and extending radially a distance fromthe outer end of the slots inwardly to the cam lows to supply andexhaust fluid relative to the displacement chambers and the slots, f. anannular array of alternate inlet and outlet ports exteNding through saidone plate in communication with the inlet and outlet recesses,respectively, g. means in the housing at the opposite face of said oneplate providing an annular inlet groove communicating with the inletports and an annular outlet groove communicating with the outlet portson rotation of the rotor and plates, and h. means creating a pressuredifferential across the sealing rollers acting in the outer ends of theslots to urge the rollers toward the cam.
 19. A rotary hydraulictranslating device as defined in claim 18, including springs in theslots urging the rollers toward the cam surface.
 20. A rotary hydraulicfluid translating device as defined in claim 18 including meansrestricting flow in and out of said recesses inwardly of said rollersduring contact of the rollers with lower portions of the cam rises andfalls, and means restricting flow in and out of said recesses outwardlyof said rollers during contact of the rollers with upper portions of thecam rises and falls.
 21. A rotary hydraulic fluid translating device asdefined in claim 20 including ports in said one plate intermediate theinlet and outlet recesses for supplying pressure to the slots in thestator radially outwardly from the sealing rollers.
 22. A rotaryhydraulic motor, comprising, a. a housing, b. a stator in the housinghaving a central cylindrical cavity and a plurality of radial slotsextending from the cavity with loosely fitting reciprocable sealingrollers therein, c. a rotor disposed in the stator cavity having aperipheral cam surface including a plurality of cam lobes andintervening lows engaging the sealing rollers to form displacementchambers, d. a pair of port plates secured to opposite sides of therotor for rotation therewith including outwardly disposed portionsslidably engaging the sides of the stator adjacent the slots andperipheral portions spaced from the surrounding housing to defineperipheral pressure chambers, e. a shaft mounted in the housing androtatable with the rotor and port plates, f. an annular array ofalternate inlet and outlet recesses in the face of each port plateadjacent the slots in the stator, g. an annular array of alternate inletand outlet ports extending through each plate in communication with therecesses in such plate, h. means providing an inlet communicating withthe inlet ports and an outlet communicating with the outlet ports onrotation of the cam and port plates, and i. said inlet and outletrecesses, said cam, said slots and said rollers being constructed torestrict flow in an out of said recesses inwardly of the rollers duringcontact of the rollers with low portions of the rises and falls of thecam, and to restrict flow in and out of said recesses outwardly of therollers during contact of the rollers with the high portions of therises and falls of the cam, thereby to create a pressure differentialacting across the rollers acting in the outer ends of the slots to urgethe rollers toward the cam.
 23. A rotary hydraulic motor as defined inclaim 22, including means for porting pressure to the slots radiallyoutwardly from the rollers intermediate the inlet and outlet recesses.24. A rotary hydraulic motor as defined in claim 23, including springmeans in the slots urging the sealing rollers toward the cam surface.25. A rotary hydraulic fluid translating device, comprising, a. ahousing, b. a stator in the housing having a cylindrical cavity and aplurality of radially disposed slots with reciprocable sealing memberstherein, c. a rotor disposed in the stator cavity having a peripheralcam surface including a plurality of cam lobes engageable with thesealing members in the stator to form displacement chambers between thelobes, d. a pair of port plates secured to opposite sides of the rotorfor rotation therewith including outwardly disposed portions slidablyengaging the stator adjacent the slots therein and peripherAl portionsspaced from the surrounding housing to define peripheral pressurechambers, e. an annular array of alternate inlet and outlet portsextending through each plate in communication with the cavity and slotsin the stator, f. a pair of pressure plates disposed respectivelyagainst the surfaces of the port plates remote from the rotor andstator, g. means at each interface of the port plates and pressureplates providing an annular inlet groove communicating with the inletports and an annular outlet groove communicating with the outlet portsas the rotor and the plates rotate, h. an inlet kidney through eachpressure plate communicating with the adjacent annular inlet groove andan outlet kidney through each pressure plate communicating with theadjacent annular outlet groove, i. means defining an annular pressurechamber behind each pressure plate in communication with the inlet porttherein and means defining an annular pressure chamber behind eachpressure plate in communication with the outlet port therein, and j.leakage paths between the stator and the rotating plates leading to theperipheral pressure chambers creating pressure in the chambers at avalue intermediate the values of inlet and outlet pressures.
 26. Arotary hydraulic fluid translating device as defined in claim 25,including passages in each port plate porting intermediate pressure fromthe peripheral chambers to the slots in the stator radially outwardlyfrom the sealing members between inlet and outlet recesses.
 27. A rotaryhydraulic fluid translating device as defined in claim 25, includingpassages through the rotor communicating the inlet ports in the two portplates with each other and communicating the outlet ports in the twoport plates with each other.
 28. A rotary hydraulic motor, comprising,a. a housing, b. a stator in the housing having a central cylindricalcavity and a plurality of radial slots extending from the cavity withloosely fitting reciprocable sealing rollers therein, c. a rotordisposed in the stator cavity having a peripheral cam surface includinga plurality of cam lobes and intervening lows engaging the sealingrollers to form displacement chambers, d. a pair of port plates securedto opposite sides of the rotor for rotation therewith includingoutwardly disposed portions slidably engaging the sides of the statoradjacent the slots and peripheral portions spaced from the surroundinghousing to define peripheral pressure chambers, e. a shaft mounted inthe housing and rotatable with the rotor and port plates, f. an annulararray of alternate inlet and outlet recesses in the face of each portplate adjacent the slots in the stator, g. an annular array of alternateinlet and outlet ports extending through each plate in communicationwith the recesses in such plate, h. a pair of pressure plates disposedrespectively against the surfaces of the port plates remote from therotor and stator, i. means at each interface of the port plates andpressure plates providing an annular inlet groove communicating with theinlet ports and an annular outlet groove communicating with the outletports as the rotor and the plates rotate, j. an inlet kidney througheach pressure plate communicating with the adjacent annular inletgroove, and an outlet kidney through each pressure plate communicatingwith the adjacent annular outlet groove, and k. means defining anannular pressure chamber behind each pressure plate in communicationwith the inlet port therein and means defining an annular pressurechamber behind each pressure plate in communication with the outlet porttherein.
 29. A rotary hydraulic motor as defined in claim 28, whereinthe alternate inlet and outlet recesses in the face of each plate extendradially a distance from the outer end of the slots in the statorinwardly to the cam lows, wherein the annular array of inlet portsthrough each port plate is radially spaced from the annUlar array ofoutlet ports through such plate and wherein the annular inlet groove ateach interface of the port plates and pressure plates is radially spacedfrom the annular outlet groove at each interface of the port plates andpressure plates.
 30. A rotary hydraulic motor as defined in claim 28,including passages through the rotor communicating the inlet recesses inthe two port plates with each other and communicating the outletrecesses in the two port plates with each other.